This invention relates to articles having a surface exposed to a flow of fluid, and more particularly to articles. for example components of power generating apparatus, having a surface over which a heated fluid flows.
Certain components of power generating apparatus, for example gas turbine engine components, operate in or are exposed to a heated stream of fluid such as air, products of combustion, etc. For example, surfaces of gas turbine engine blading members (including airfoils of blades and vanes), struts, and engine internal fluid-flow passages, downstream of the combustor section, are heated by a flow of fluid, including air and products of combustion, within the engine. From an engine design standpoint it is desirable to operate the engine at relatively high temperatures. Sometimes such temperatures are higher than certain metal alloys from which components are made can withstand efficiently. In such a case, components require cooling or heat dissipation from a surface to maintain component temperatures within acceptable ranges. In other situations, such cooling is required to maintain proper thermal matches between cooperating components for clearance or stress control, as is well known in the art.
To improve the overall cooling effectiveness of a component, it is desirable to have a large heat transfer surface area, particularly on the fluid flow surface exposed to a fluid that acts as a coolant. Therefore, it has been proposed to apply to, or generate in, an article surface turbulators for heat dissipation from a component. In general, turbulators are protuberances disposed on a surface to enhance heat transfer from the surface. For example, articles having turbulation, and methods for providing turbulation are described in copending U.S. patent application Ser. No. 09/304276xe2x80x94Hasz et al, filed May 3, 1999. Relationships between heat transfer from a surface and turbulator profile and spacing have been reported in xe2x80x9cEffects of Turbulator Profile and Spacing on Heat Transfer and Friction in a Channelxe2x80x9d by Taslim and Spring, (Journal of Thermophysics and Heat Transfer, Vol. 8, No. 3, July-September 1994). Impingement cooling of a textured surface of a gas turbine engine assembly is described in U.S. Pat. No. 5,353,865xe2x80x94Adiutori et al. (patented Oct. 11, 1994).
Heat transfer improvement from a surface including particles as turbulators is significant. However, it is desirable to have more accurate control of turbulator surface area for heat transfer from a surface, and accurate turbulator positioning and bonding to a surface. In addition, improvement of article surface strength and/or control flow of fluid across a surface with a turbulator can improve component life and efficiency.
In one form, the present invention provides an article comprising an article surface, and a plurality of discrete metal wires bonded lengthwise of the wires along the article surface. In one embodiment, the metal wires are in the form of woven wires or wire meshes. In another embodiment, the article is a tape, for example a brazing tape, comprising a base and the plurality of metal wires carried by the base.
In still another form, the present invention provides a method for enhancing a surface an article, for example an engine service operated article, comprising bonding a plurality of discrete metal wires lengthwise of the wires along a surface of the article.